Pinion contacting axle housing

[Farabomb]

I searched but I didn't see anything that directly addressed it so I'm sorry if this question has been asked before.

I was installing the hot racing lockers yesterday and I noticed that the front pinion made contact with the inside of the axle housing and chewed it up a bit. I'm running the new castle sensored brushless crawler 3800kv with a mamba x on 3s. I have traxxas bushings instead of bearings with 43/13 rear and 36/14 in the front.

Somewhere in my reading I saw something about over/under not being a good idea with brushless. I just skimmed and I can't find the thread again in case it explained why. The front was a bit bound up so I can see that causing deflection and contact with the housing. Could the gearing not be helping the situation?

I have a SCX10 with over/under as well but I'd like to know before I tear them both apart again if having matched diff gears prevent this happening again. I know brushless will break stuff. I've gone as far as I can before going to truly bulletproof measures. I don't plan on beating on it too hard but should I be ordering up some new big bearing housings and do it once?

[altd896]

The full split of over/under isn't such a good idea on say a race truck like a U4 rig but if your geared down & crawling/trailing mainly, the fact your brushless shouldn't matter with the split ratios.

It's unlikely to be the over/under causing the pinion to touch. Remember they are only moulded plastic & they won't be exactly 100%.
I've had one that was hard to get that inner bearing to seat right in & others than need shims to push the pinion/bearing out to the ring gear.
I ran the bronze bushes for a while but found they wore pretty quick, a change to Boca or Acer bearings have since been fine, even in racing trucks.
I shim my lockers & pinons to get them nice & snug, the pinion can float a bit more than is ideal otherwise.
The 8x11 will move the pinion bearing in the housing https://www.amainhobbies.com/yokomo-...c-s80s/p270534
the 5x8 will move the pinion out of the bearing https://www.amainhobbies.com/yokomo-...c-s50s/p270533
& the 10mm you can push the spool https://www.amainhobbies.com/yokomo-...-s100s/p242340

Also handy to take a bit of the slop & axle float out of the knuckles

[Farabomb]

Those links help a lot. I was at the LHS last week and we were having a tough time tracking down shim part #'s. I may have to make a call to Amain today if the LHS can't source them. I replaced the pinion bushings when it was in there just to be safe. the inner one (gear side) actually had a ridge and it was a bit tough to get off. The cross pin hole had a burr on it as well that needed to be sanded before installing the new ones. I'm thinking it was because it was bound and I tried to power it out instead of walking over to get it out of the stream it was stuck in.

I have the day off and it's thunderstorms all day so I'm going to tear it down again and see if there is any more damage from running it yesterday. I also am going to conformal coat the sensor wire as the dielectric grease didn't do an amazing job of sealing it.

What cleans off dielectric grease completely? I've tried some water based cleaner like 409 as well as motor spray and isopropyl alcohol but it doesn't seem to be coming fully off. The conformal coating needs a clean and moisture free surface to work properly. I really don't want to be cleaning that stuff off if it doesn't work the first time.

[ferp420]

I found thrust bearings work great the bushings ware out fast and the bearings go pop the first time i goose the throtle the thrust bearings seem to be holding though ive got about 6 months of daily abuse on my front thrust bearing and its still going strong

[Farabomb]

Any chance you have a link to the thrust bearings you are using? I can see how a thrust bearing might be better suited.

I don't mind the bushing wearing out. I'll take that over bearing failure and possibly taking out other parts.

If you're wondering, alcohol doesn't seem to break down dielectric grease all that well. When blowing out my sensor wire gobs of it came out. I don't have acetone or other solvents in the house so I've moved on to tamiya paint thinner to see if that works better.

[ferp420]

I got my first one from super shafty and my second one from ebay ebay will be cheaper but 3+ months is a long wait its a great option on the cheap the big bearing housings are a bit more $ but are saposed to hold up realy well to

[Farabomb]

I'll take a look at my local bearing place and see if they have them. They have everything else.

It didn't seem to make contact after the new bushings. Maybe it was because it was bound up pretty good and I thought throttle alone would get me out.

[Farabomb]

Got a new axle, swapped out the poop hot racing spools with the setscrews for some quality incision ones. New bushings, shimmed tight on the gear side assembled it with some STRC bearing retainers and diff covers. Went for a run today and I noticed the pinion on the front axle was hot and the sideplay was more than when I put it together. Went home and there was minor contact this time. I'm running stock hardened in the front and UD hardened in the rear.

1: Is the gearing difference putting too much strain with the 3800kv?

2: Could the pinion been a bit too snug and heated the bushing enough to let it deflect?

3: The 3800 kv too much motor and I should dial some power out in castle link?

4: The axle just needs a larger inner bearing to deal with the loads?

1a: Run underdrive in both axles. I believe I have a UD set in the rear of my SCX10

2a: Shim less or just leave it as is and hope it's worked it's way happy. Do I go back to running bearings in the front to not have to worry about friction heating?

4a: Wait till axial replishes their stock of axles so D_lux can mod some more for us.

[altd896]

Have you got pics in the housing with it apart?
I don't quite follow where the pinon is contacting the housing.
Bushing will always run hotter than a bearing & once it's worn it'll have slop, I was never impressed with how quick the traxxas bushing I had wore & went back to bearings.
I still don't see the 3800 being the problem.

[Farabomb]

When I get home I can take a pic of the old one I took out. Imagine the pinion deflecting vertically coming in contact with the plastic around it. It's like the axle is bound up and the pinion is climbing up the ring gear and making contact at the top. There is also a little bit on the bottom as well like it was trying to climb down it.

I did roll it on it's lid and I tried to get it back over with throttle and reverse. I only did that for 15 seconds before I thought better about it. I ended up walking my crippled ass over and that's when I noticed the hot pinion. I have a badly torn patella tendon so the less walking the better.

I have a feeling I'll tear it apart again and replace the bushings with bearings tonight. It's strange it's only on the front axle that I'm having issues. I wonder if the weight I have in the rims is not helping.

[84yoda]

This has been discussed soooo many times its ridiculous.

5x13 bearing in stock housing or 5x13/5x14 in an aluminum housing is the fix.

End of story.

[Farabomb]

I understand it's been discussed at length, I've read the threads. I'd love to get a plastic housing with a 5x13 but they're not presently available and I lack the tools to do it myself.

Why is only the front doing it? The back hasn't been an issue.

[ferp420]

When i was running stock plastic housings brand new everything incision locker new hd gears new housing new bearings all shimed tight i was still skipping teeth the plastic housings just dont hold up to big power also if your jumping it with waited wheels the housing is gona flex ive chiped gears doing that went to pot.metal housings it took a while to find the right combo but it was worth it if i have any more issues ill hog out my axle for the bigger bearing but as of now the thrust bearing is working up front but wouldent fit in the rear housing for what ever reason lol

[84yoda]

The heat is probably causing the plastic to be softer and letting the pinion contact the housing.

Also OD gears are a bad idea because they have the worse gear mesh and puts more strain on everything. UD front/rear is the way to go, best gear mesh and less strain on drivetrain.

[Farabomb]

I have the UD in the rear already and I may pick up another set today just to see if that helps.

I am a bit pissed with all the screwing and unscrewing I managed to strip the threads one of the bearing caps. Brand new axle and I was using a torque limiting driver.

[Farabomb]

In searching for a fix for my stripped bearing cap issue has anyone used a threaded insert successfully? I found some m3 threaded inserts that might work. I'll have to check how much room there is when I get home.

https://www.amazon.com/a16041800ux08...FPACNXM9B7SFG8

Edit: Also found these guys so one way or the other I should be able to get it to work.

https://www.amazon.com/uxcell-Helico...s=3mm+helicoil

[84yoda]

I've used some 4-40 from mcmaster before.

Why not just buy a new housing? There cheap enough. With buying inserts and time installing, a new housing is worth it.

[Farabomb]

That is on the brand new housing I have. I did notice my LHS has one in stock so I might pick that up tomorrow. The KNK machine thread I have in there now seems to hold well enough but I'm still going to try the inserts because it's only a matter of time before they totally let go. If they work I'll end up doing all the bearing caps on all the axles I have and try to mill out for a larger bearing on the wasted one.

Here is a picture showing the contact on the old housing. It's probably salvageable if I can get my hands on a drill press and a 13mm endmill. I put my caliper on the old axle and while the brass inserts could work I think drilling and tapping for the coils would be easier and the safer way to go.

[altd896]

I'm wondering if the contact with the housing is simply the OD pinion having a larger diameter?
I don't have one apart to measure but just going visually off online pics the OD pinion definitely looks larger to me.

There's certainly advantages to having the OD/UD split that makes it worth keeping if you can.
They have a 5x14 bearing in the AR44 housing, if they're going to keep the AR60 in production it's about time Axial get a collar added to their inner mold so at least the inside bearing is bigger, even if only 5x13

[Farabomb]

I just ordered the helicoils and the 13mm endmill. I texted my friend at the LHS to hold the AR60 they have on the wall for me just in case.

The front has the stock ratio hardened gears in it, the rear has the UD. If anything the UD uses a 14 tooth I believe so that would be bigger and more risk of contact. I went back to bearings and shimmed tight but I haven't had time to go run it. Last time I did I couldn't walk for 2 days. Having an almost fully torn patella tendon really sucks.